Partial
A component of the sound spectrum.
What it means
Partials are the individual components of a sound. A vibrating body vibrates not only as a whole but at the same time in halves, thirds, and further parts; each of these partial vibrations corresponds to a tone. The first partial is the fundamental, which the perceived pitch follows; those above it are called overtones. Together they form the overtone series.
Musical use
Which partials come to the fore and how strongly determines the timbre. Sounds with many strong high partials seem bright and cutting, those with few soft and round; individual instruments have characteristic distributions by which they can be recognized. Within one instrument the ratio also changes with register and dynamics — loud playing usually brings out more high partials, which is why loudness and timbre are connected.
Two things follow from this for ensemble playing. First, purity: when two notes form a pure interval, their partials coincide, the beats stop, and the sound becomes calm. Second, blend: two instruments whose partials complement each other merge into a new colour — the art of orchestration rests on this.
Not all partials can be represented in the usual tone system; individual ones, for instance the seventh, deviate noticeably. With bells and some percussion instruments, moreover, the partials do not lie in whole-number ratios, which is why their pitch is hard to determine.
Bear in mind that a natural sound consists of many partials. If they are whole-number multiples of the fundamental, one speaks of harmonic partials or overtones. With bells, timpani, and metallophones they often lie inharmonically, which makes up the particular sound of these instruments. Their distribution and strength shape the timbre; as a note attacks, some partials come out earlier than others.
Performance practice
Work on timbre through the embouchure or attack — it decides which partials speak. String players can play harmonics to make individual partials audible; this sharpens the inner conception. And tune by the disappearance of the beats: when the combined sound becomes calm, the partials coincide.